1. Field of the Invention
The invention relates to a method and apparatus for effecting the packing of the annulus defined between one or more tubing strings and the casing bore of a subterranean well.
2. History of the Prior Art
In a typical dual well string installation, a packer is into and set within the well bore to close off the space about both strings above an upper production zone, and another packer beneath the dual packer and the lower end of one of the strings (known as the "short string") is lowered with the other string (known as the "long string") to seal thereabout below the upper zone but above the lower production zone. Thus, oil or gas from the upper zone is produced through the short string, and oil or gas from the lower zone is produced through the long string. As shown, for example, in U.S. Pat. No. 3,414,058, as well as on page 865 of the "1982-1983 Composite Catalogue of Oil Field Equipment and Services", dual string packers of this type normally comprise body means on which a packing element is supported and about which a slip assembly is carried, together with a pair of mandrels extending vertically within the body means and through side by side holes in the packing element so that each may be connected as a part of one of the well strings. Ordinarily, one of the mandrels is adapted to be temporarily closed so that, with the packer lowered to the desired position, hydraulic fluid may be supplied through the one mandrel to fluid pressure responsive means on the body means for causing relative vertical movement between sections of the body means above and below the packing element and slip assembly in order to move them into engagement with the well bore. See also U.S. Pat. Nos. 3,098,524; 3,211,226; 3,299,959; 3,658,127 and 4,505,332.
Packers of this type are not only expensive to manufacture but also time consuming to install since the upper portions of both tubing strings must be individually lowered into place. The provision of a separate body upon which the packing element is supported and about which the slip assembly is carried is a prime factor in raising the cost of manufacture of such prior art packers. Furthermore, such packers are characterized by a reduction in fluid passage area for at least one of the mandrels traversing the body of the packer. Any reduction in fluid passage area for a tubing string is obviously an undesired limitation on the use and productivity of the packer.